1. Field of the Invention
This invention relates generally to nanoscale three-dimensional battery architecture which can accommodate various combinations of new electrode materials, electrolytes and wiring configurations in order to optimize battery performance, and more particularly to a three-dimensional nanobattery system having individually wired nanostructured anode and cathode electrodes with conductive nanowires and a thin, intermediate layer of an electrolyte.
2. Description of the Related Art
The potential of nanotechnology to provide new technological breakthroughs is the object of much current attention. Nanostructured materials have the potential for enhanced properties and efficiency improvements in virtually every area of science and technology through enhanced surface areas and quantum-scale reactions. This disclosure deals with the formation of novel nanoscale structures that have numerous potentially important applications.
An example of an application for nanotube structures is found in Assignee's U.S. Pat. No. 6,586,133 for “Nano-Battery Systems” issued Jul. 1, 2003. The patented disclosure is directed to nano-batteries and micro-batteries as well as their manufacture and use. Porous substrate technology is utilized wherein the substrate has a plurality of holes or pores that range in diameter between ten (10) micrometers to one (1) nanometer (nm).
Nanoscale or microscale deposition of particles by a sputtering process is also known. The process of sputtering may be defined as the ejection of particles from a condensed-matter target due to the impingement of energetic projectile particles. Operatively, the source of coating material, referred to as the target, is mounted opposite to the sample, in this case a porous substrate in a vacuum chamber. The most common method of generating ion bombardment is to backfill the evacuated chamber with a continual flow of gas and establish a glow discharge, indicating that ionization is occurring. A negative potential applied to the target causes it to be bombarded with positive-ions while the substrate is kept grounded. Impingement of the positive-ion projectile results in ejection of target atoms or molecules and their deposition on the substrate.
One of the most useful characteristics of the sputtering process is its universality: virtually any material is a coating candidate. Sputtering systems assume an almost unlimited variety of configurations, depending on the desired application. DC discharge methods are often used for sputtering metals, while an RF potential is used for less conductive materials. Ion-beam sources can also be used. Targets may be elements, alloys, or compounds, in either doped or undoped forms, and can be employed simultaneously or sequentially. The substrate may be electrically biased so that it too undergoes ion bombardment. A reactive gas may be used to introduce one of the coating constituents into the chamber, i.e. oxygen to combine with sputtered tin to form tin oxide (reactive sputtering).
A nanostructure fabricated by RF sputtering of barium strontium titanate (BST) on porous alumina substrates suggests that the sputtered material does not penetrate into pores, but rather preferentially gathers along the continuous circular edge of pore openings. These types of sputtered metal structure or “antidots” are not partially or complete capped, are not layered, are formed only from metals, and are not used to assemble any type device.
Nanotubes and other nanostructures may be formed as large arrays, and in this form are often referred to as nanoporous or mesoporous structures. “Meso-porous” tin oxide structures have been created using surfactant templating techniques. The resultant material, however, consists of material containing irregular nanopores averaging about two (2) nm in size, without long-range order. These nanoporous or mesoporus structures cannot be formed in large arrays of tunable pore sizes, which develop wall height as well as porosity, and also cannot be partially or completely capped to form a nanobasket structure.
Accordingly, it is desirable to produce a nanotube structure wherein at least one end of a nanotube is partially or completely closed or covered over so that the nanotube forms a nanobasket.
It is further desirable to use sputter deposition techniques to create partially or completely capped and/or layered nanotube structure, which opens a wide range of potential applications.
It is still further desirable to utilize a substructure of very small nanoparticles, i.e., the walls and caps of the basket are themselves composed of nanoparticles ten (10) nm and less in size. Numerous scientific studies attest to the importance of nanoparticulate grain size in performance characteristics of electronic, optical, and catalytic devices.
It is yet further desirable to form a large array of nanobaskets as a nanoporous architecture, such as for use in battery systems.
The assembly of individual nanostructured components into a three-dimensional battery system has been proposed as the means to promote ion diffusion in electrode materials by substantially increasing the effective electrode surface area to improve energy per unit area characteristics and promote a high rate charge/discharge capacity. Such features should enhance general battery performance, but they are of particular importance for thin film batteries and nanobatteries able to power proposed micro and nano electromechanical systems (MEMS and NEMS). Recent work on three-dimensional architectures for improved performance includes rods or “posts” connected to a substrate, graphite meshes and films of cathode, electrolyte and anode materials lining microchannels in an inert substrate.
The nanoscale three-dimensional battery architecture disclosed herein represents a novel approach from other proposed solutions by focusing on a negative space (the hollow portion within the nanobaskets) rather than on a positive-space structure such as a rod, post, mesh or film. While multiple three-dimensional battery architectures have been proposed, no prior configurations are based upon the individual wiring of hollow nanobaskets nor has a working three-dimensional nanobattery been claimed.
It is therefore desirable to provide a three-dimensional nanobattery formed by individually wiring nanobasket structured electrodes and combining them with an electrolyte. Short, capped nanotubes, i.e., nanobaskets, may be formed by RF-magnetron sputtering onto nanoporous templates, and metallic nanowires are grown, such as by electrochemical deposition, from the nanobaskets. The same procedure can be used to fabricate both a battery anode and a battery cathode, and a thin layer of electrolyte is placed between the two nanobasket electrodes. The nanobattery circuitry may be completed by contacting the ends of the nanowires opposing the electrolyte with a conductor, such as a metal plate.
It is further desirable to provide a three-dimensional nanobattery architecture that promotes ion diffusion in electrode materials by substantially increasing the effective electrode surface area to improve energy per unit area characteristics and promote a high rate charge/discharge capacity.
It is still further desirable to provide a nanoscale three-dimensional battery architecture for thin film batteries and nanobatteries, which would be able to power proposed micro- and nano-electromechanical systems (MEMS and NEMS), or used in massive arrays in place of conventional batteries.
It is yet further desirable to provide a nanoscale three-dimensional battery architecture based upon individual wiring of hollow nanostructures and that represents a robust nanoarchitecture that accommodates a variety of electrode and electrolyte types.